1. Field of the Invention
The invention relates generally to a device configuration and method of manufacturing an insulated gate bipolar transistor (IGBT). More particularly, this invention relates to an improved IGBT device configuration and manufacturing method for a trench IGBT that has a monolithic deep body clamp diode for preventing latch-up, and allowing reverse current to flow through the diode when the IGBT is turned off in many power switching applications such as inverter and H-Bridge motor switching circuits.
2. Description of the Relevant Art
Conventional device configuration and manufacturing methods for providing the insulated gate bipolar transistor (IGBT) devices are often confronted with two technical difficulties. FIG. 1 illustrates the first technical difficulties of latch-up due to the intrinsic parasitic thyristor formed as NPN and PNP transistors formed in parallel across the collector and emitter. The second technical difficulty is the slow switching speed due to operations of current conduction that involves two electric carriers, i.e., injection of electrons from the N+ emitter and holes from the P+ emitter. After the gate is turned off, the holes move to the body regions but the electrons become extra charged carriers due to shut off of the channel regions. The IGBT device cannot be turned off completely with these extra charged carriers until the extra electrons are combined with holes to achieve significant current reduction. The switching speed of the IGBT devices is adversely affected due to these extra charged carries after turning off the gate.
As a key component in the power electronic systems, the semiconductor power devices are commonly implemented in the power electronic systems such as the power systems for the hybrid, electric or fuel cells vehicles. Recently, there are increasing demands for high performance semiconductor power devices. Particularly, there are increasing demands for high performance high voltage semiconductor power devices such as the insulated gate bipolar transistor (IGBT) devices. However, conventional high voltage semiconductor power devices such as the insulated gate bipolar transistor (IGBT) devices are still confronted with the technical difficulties caused by an increased collector-emitter saturation voltage. The increase of collector-emitter saturation voltage becomes even more pronounced when the IGBT is manufactured with further miniaturized size to increase the cell density of semiconductor power device.
Park discloses in U.S. Pat. Nos. 5,702,961 and 6,051,850 a planar IGBT having built-in freewheeling diodes as shown in FIG. 1. The IGBT device includes an n+ type buffer layer 116, an n-type base layer 104 having a high resistivity, and a deep p-type base layer 108 are formed in the order mentioned on one surface region of a p+ collector layer 102. Also, an n+ emitter layer 110 formed in a part of the surface region of the deep p-type base layer 108. An integral diode comprises deep base 108 and N+ 100.
The IGBT disclosed by Park has a disadvantage due to the deep P base region 108 that is deeper than the base region. This device configuration with a deep base region causes a high JFET resistance between two adjacent contact trenches. The higher JFET resistance further leads to an increase in the collector-emitter saturation voltage. Moreover, the planar IGBT device disclosed by Park has a poor electron injection efficiency due to the current path in a planar IGBT wherein the electrons have to pass through a channel region laterally, and the electrons are transmitted through the JFET region vertically then into drift region.
Therefore, a need still exists in the art of power semiconductor device design and manufacture to provide new manufacturing method and device configuration in forming the semiconductor power devices such that the above discussed problems and limitations can be resolved.